Disclaimer: This is a not so long but very dense text, like most of what I write. You can't just glance your eyes to read it.
I am a former programmer, a person who proposes to work hard to simplify computer processes. And I think most of us overlook "simplicity" way too much. I know I did overlook it many times, and I probably still do, despite all my efforts.
I'm currently struggling a lot on finding a perfect and simple solution for "bookmarking", in lack of a better term. It's not just bookmarking, though, as that implies having broken links. I want no missing data. So I want to save an offline / personal copy for at least 10 years. Know when I saw it. Share it. Search with keywords or date. Browse thumbnails. Etc.
I've tried delicious, google bookmark and +1, old extinct xmarks and its new lastpass version, all those tools you associate with "bookmark". But I'm also using dropbox, calendar, twitter, youtube history, ifttt, just to give you some examples and maybe an idea of what I actually mean and what I actually want to find. Maybe there is such a tool out there, but it's certainly not associated enough with the whole bookmarking concept and I still couldn't find it after a couple of days.
For another instance, I'm also recently struggling to find an awesome text editor. Yeah. Your read it right. Text editor. Awesome one. Offline. Collaborative. Powerfull. Reliable. Clean. It doesn't exist. Not yet. Not anything close to it. When I started searching for one, I thought I'd be able to find one easily. I overlooked it.
Now going back some years... since my first smartphone, an iPhone 3GS, I can't find a phone that will give me all the simple things I want. Share files. Hear music. Record callings. Battery life. Among others. I hardly can believe how this also doesn't exist yet. Even Apple, being so good with keeping a checklist, still couldn't do it. I currently own a Moto Razr HD, which still lacks power on all "simplicity" I've mentioned there, but at least it works much better (in general) than any iPhone ever did, for those "simple" tasks. Granted, gadgets are way more complicated to build than software. I'm just trying to explain in general terms what "simple" means to me, and why it is indeed difficult to build "simple" stuff. And I think Apple, Google and even Nintendo are masters at doing that, in general.
With that, I hope you can now see there are lots of difficulties in being "simple"!
I think the most important one is: "simple" isn't opposite to "complex", which isn't synonymous of "complicated". We constantly develop technology to simplify things for us, since the first wheel or pen. But the more it simplifies, the more complex it needs to be. And building up a solid complex tool for us, highly subjective individuals, is quite complicated.
Even building something apparently as simple as a bookmarking tool is something extremely complex. Extremely. That is if you have the degree of exigence I do.
So...
If you are doing any attempt to build up technology to simplify our lives, please, take a step back. Look at the whole picture. As most of us usually do, you're also probably doing it wrong. I believe for some people all it takes to do it right is just being more careful.
For Apple, the iPhone is actually very close to the whole "simple" concept I try to explain here. But almost all of its issues are actually limited thanks to some legal issue. All, except battery. Just make a bigger phone with a smaller screen! Call it "iPhone Pro". Not everyone uses it so much, but for lot of us who do, we care about it lasting a whole day with heavy usage more than anything else.
For me, I know I'm so bad at it I just gave up on trying. Just hope this isn't too hypocritical.

I could only figure out what you meant there because of your splitted question in portuguese.

You ask for the title, again. Good catch.

It's a question without an answer. A simple one at least!

Almost all of our information technology (what people call tech) usually is far from simple and there is no single reason for it.

Maybe we could call it stupidity, but humans are not that stupid. We're more like lost in the middle.

We could call it too much information. The world have about 8 to 9 billion people. That's a fucking lot more than our weak brain can process. We can only really humanize about 150 people. So in here I'm also blaming the brain capacity, but that's what computers are made for - to help minimize that impact.

We could even call it a social issue in which we're not really allowed or encouraged to use tech. It's too nerdy, don't do that, our brain is capable enough and "we only use 10%" right? Not really.

Why is it so difficult? Because it is. Maybe a better title would be "It is so difficult for a technology to be simple. Why, oh why?!". Like an airplane crashing, there are just too many variables to choose only 1 to blame. We must not.